The present disclosure generally relates to processing particles in liquid biological samples for analytical purposes and, in particular, relates to an automated system for processing such particles with a rotatable vessel comprising a lateral collection chamber and to a method for processing particles in liquid biological samples.
Analytical applications for particles such as cells or artificial particles, especially in the field of clinical diagnostics, include flow cytometry, microscopy, cell counting, harvesting cells for or from cell cultures, and the like. Analytical methods for target molecules isolated with the help of binding particles are, for example, amplification and detection of nucleic acids such as RNA, DNA, mRNA (by means of PCR or other amplification techniques), ELISA or electro- or chemiluminescence assays for proteins, and the like.
A variety of different approaches have been taken to facilitate processing of such particles. For instance, classical centrifugation in which particles are typically sedimented at the bottom of tubes usually requires bulky centrifuges that take up a considerable amount of space in a clinical or other laboratory. Furthermore, retrieval of the supernatant after centrifugation may be hampered by the fact that a pipette or its tip should not touch and thus disturb the particle pellet at the bottom of the tube. Hence, the pipette or tip may not be inserted all the way to the bottom of the tube, resulting in a residual “dead” volume being a potential source for impurities or inhibitors of subsequent chemical reaction. This circumstance also impedes efficient automation of particle processing. Besides, usually batch processes are used, and the often large centrifuges imply relatively long distances for sedimentation, effectively slowing down the process. One variant of an automated device for processing particles is a test tube containing blood cells is mounted on a rotatable spindle, the latter including central passageways for the introduction of wash fluid and air into the test tube, and radial exit passageways at the bottom of the spindle. A vacuum is applied to the exit passageways so cell supernatant is aspirated out through them. This setup requires an intricate set of fluid and gas connections, and means for applying positive or negative pressure, thus complicating assembly as well as usability of such a system.
The likewise widely-used approach relying on filters for retaining particles is also not well amenable to automation, especially in view of the fact that the re-suspension of particles mostly requires manual steps.
In other systems in the field, the particles to be processed are bound to magnetic beads, or the particles themselves have magnetic properties. While this technology has been automated in the art, various problems have been encountered, such as clotting of magnetic beads resulting in dead volumes, or disturbance of downstream applications due to the presence of magnetic beads. Furthermore, respective automated system all require a magnet which takes up space and still needs to be brought into the close vicinity of a vessel or pipette holding the magnetic beads or particles, raising the need for complicated geometrical solutions and reducing flexibility when designing a respective automated system for processing particles.
Microfluidic devices, as an alternative technology used in the art, allow particle processing by exploiting the particles' hydrodynamic properties. Such devices usually contain microstructures of about 5 to 100 μm. It is, however, difficult to attain to a sufficient volume of such systems in order to permit medium to high throughput, as increasingly required in the clinical diagnostic environment, especially in terms of processed volume per time.
Generally, the automated processing of particles is relatively complex and requires a considerable number of distinct processing steps, with each step requiring its own instrument structure(s). Such steps include retaining particles in suspension, separation of particles, removal of supernatant from separated particles, re-suspension of particles, optical analysis of the particles, and the like.
Therefore, there is a need for an automated system that reduces the complexity of known automated system and also minimizes, or even abolishes, the need for manual intervention, thus contributing to cost efficiency, usability and increased throughput of the system.